In the paper the creative causes and protective measures to the instant false alarm, which is one of the types of false alarms taking place in the BIT(Built In Test) system of electronics or weapon equipments, are analyzed. The basic theories of grey correlation and fuzzy neamess are offered in order to identify the instant false alarm. The environment al samples group(which are parameters of the temperature, humidity, power or vibration)and instant false alarm sample(which is due to the suddenly varying of vibration or power parameter) are got by both computer and physical simulation. Those samples are analyzed according to the measures of grey correlation and fuzzy neamess, the relationship between the sudden varying of vibration or power parameter and the instant false alarm are identifed. The results testify that the measures offered in the paper are practical in the recognization the instant false alarm.